Swap Studio is an AI-powered character transformation workbench that uses motion capture and video synthesis to replace a person in a video with any character of their choosing. Users record themselves directly from the browser or upload an existing clip, provide a character image, and the system generates a new video in which the character takes their place while preserving exact movements, gestures, and timing. Built by Roman Slack, the tool is positioned as a way to access powerful video-synthesis models through their direct APIs rather than paying marked-up middleman services.
The application offers three distinct transformation modes. Character Swap replaces the person in a video with a supplied character image while keeping movement and scene context intact. Motion Control animates a static character image using motion extracted from a reference video, with an optional text prompt to guide the result. Lip Sync synchronizes a video's mouth movements to match a provided audio track. Quality can be tuned between Standard and Pro modes to balance fidelity against cost.
Under the hood, Swap Studio pairs a Next.js 15, React 19, and TypeScript frontend with a Python FastAPI backend served by Uvicorn. It integrates multiple AI providers, including fal.ai for Character Swap and Lip Sync, Replicate for Motion Control, and the Kling Direct API for longer-duration generations. FFmpeg handles automatic video compression to optimize uploads, and the backend exposes a job-based REST API with real-time progress updates, status polling, and cancellation. Transparent per-provider pricing and documented duration limits make the cost and quality tradeoffs clear to users.
Key Features
- Character Swap mode that replaces a person in a video with any character image while preserving movement
- Motion Control mode that animates a static character image from a reference video
- Lip Sync mode that synchronizes mouth movements to provided audio
- Browser-based webcam recording (3-30 seconds) plus video upload with drag and drop
- Standard and Pro quality options for different quality and cost tradeoffs
- Automatic FFmpeg video compression for optimal API uploads
- Real-time progress updates with job status polling and cancellation
Tech Stack
Designed and built by Roman Slack, Lead AI Platform Engineer. See more of Roman Slack's work on the projects page or get in touch via the contact page.